This invention relates to photochlorination of methyl aromatic compounds.
Photochlorination of methyl aromatic compounds such as toluene, o- or p-toluenesulfonyl chloride, 3-chloro-4-methylbenzenesulfonyl chloride, and o-, m- or p-xylenesulfonyl chlorides, is known. See for example British Pat. No. 956,857; British Pat. No. 1,401,038; U.S. Pat. No. 3,230,268; Miller et al., "The Displacement of Aromatic Substituents by Halogen Atoms", Journal of the American Chemical Society, Vol. 79, pp. 4187-4191 (1957); and Miller, "A Regiospecific Synthesis of 4-Chloroalkylbenzenes", Journal of Organic Chemistry, Vol. 38, No. 6, pp. 1243-1245 (1973). Although good yields of certain chlorinated products have been reported, the time required to produce chlorinated products, in which the benzylic hydrogens have each been replaced by chlorine, are unduly long.
It would therefore be highly desirable to provide a photochlorination process wherein reasonable yields of methyl aromatic products exhibiting total benzylic hydrogen displacement by chlorine is achieved in reduced reaction times.